信噪比

And the effects of length of data N to the approximate entropy of chaotic system isalso analyzed.All these are accomplished by examining several time series produced by a surperposition of white noise and noise-free data.It uses the discrete system logistic map and continuous system Lorenz attractoras the examples.

以Logistic方程描述的离散系统和Lorenz方程描述的连续系统为例，采用白噪声和无噪声信号以不同的信噪比混迭而成数据的方法，分析了相同数据长度N，不同信噪比下，混沌系统近似熵的变化；相同信噪比，不同数据长度对系统近似熵的影响。

On the contrary, in this frequence point the S/N ratio maybe lower.

由于地震数据不同频段有不同的信噪比，常规的去噪方法对信噪比低于一定程度的频率成分就起不到压制噪声的作用，相反，在这样的频率点可能还会降低信噪比。

This thesis mainly discuss following issues, Theory and simple expressions for array covariance matrixes are derived when angular spread functions are symmetric distribution functions, i. e. the Uniform distribution, the Gauss distribution, the Laplace distribution and the Von Mises distribution, and a non-symmetric distribution function, i. e. the Gamma distribution. And the relation between the effective signal subspace and the array number, or and the nominal angle of the distributed source, the angular spread, the distributed functions, and the Signal-to-Noise Ratio is gained. The dimension of the effective signal subspace increases with increment of the array number. And it is more obvious to the non-symmetric distribution. The dimension of the effective signal subspace decreases with increment of the nominal angle. And the distributed source is equal to a point source as θ=π/2. The dimension of the effective signal subspace increases with increment of the angular spread.

本论文针对阵列信号处理中广泛存在的分布源现象，主要讨论了以下问题：推导了角度分布函数分别为对称的均匀分布、高斯分布、拉普拉斯分布、Von Mises分布和非对称的伽马分布时，分布源阵列接收信号协方差阵的严格模型和简化模型，得到了单个分布源的有效信号子空间随阵元数、分布源中心角、分布角、角度分布函数和信噪比的变化规律：随着阵元数的增加，对所有角度分布函数的有效信号子空间维数也随着增加，且非对称分布函数的有效信号子空间充满整个空间的可能性更大；随着分布源中心角逐步增加，有效信号子空间维数逐步减小，当θ=π/2时，等价于点源情形；随着分布源分布角逐渐加大，有效信号子空间维数也随之增加，直到有效信号子空间充满整个空间；随着信噪比的增加，有效信号子空间维数有一定程度的减少。

In this case, the received carrier is modulated by unknown Doppler frequency and frequency rate. The estimation techniques as maximum likelihood estimator and extended Kalman filter are described and compared in our dissertation by tracking a common simulated highdynamic trajectory.

文中详细推导了任意信噪比情况下，时延和多普勒频率估计的方差下限表达式：在信噪比高于门限信噪比的情况下，具体推导了估计方差的Cramer-Rao限；在信噪比低于门限信噪比时，估计的方差下限还与失锁概率有关。

Correlation and signal-to-noise ratio of the space sources can affect the resolution of DOA estimation of subspace algorithms. Using this relation, the algorithm changes the correlation and SNR of the equivalent sources by processing the Toeplitz matrix based on the Toep-MUSIC algorithm, so that the resolution of DOA estimation can be improved.

改进算法利用信源间相关性和信噪比对子空间类DOA估计算法分辨力的影响，在Toep-MUSIC算法基础上，通过对Toeplitz重构矩阵的处理，改变了等效信源的相关系数和信噪比，从而使DOA估计分辨力得到提高。

To estimate the high signal to noise ratio in every recorded trace using quantitative method and erase the recorded traces with low signal to noise ratio so as to form a standard trace with high signal to noise ratio.

在形成标准道时，利用定量估计信噪比的方法，对每个记录道分段进行信噪比估计，剔除信噪比低的记录段从而形成高信噪比的标准道。

Firstly, a simple closed-form MIMO channel capacity formula is derived by using the eigenvalue distribution of Wishart matrix.

首先，利用Wishart矩阵的特征值分布，导出了一个简单闭合的MIMO信道容量公式；然后基于此公式，得到了MIMO信道容量在高信噪比时的渐近界，解析地反映了随着信噪比的逐渐增加，MIMO信道容量与信噪比和收发天线数目的最小值呈渐近的线性关系；最后，计算机仿真验证了所提出的MIMO信道容量公式及其渐近界的正确性。

Increasing the input noise may increase the signal-to-noise ratio of the output response V(t within the element's parameter region indicating that the periodic components of V increase as the input noise increases. The relationsip between the variation of the SNR of the V curve and the noise is similar to the that of the resonance.

结果表明：在一定的条件下，增大输入噪声的值不仅不降低输出响应信噪比；反而迅速增加输出响应的信噪比，使输出响应中周期信号的分量反而加强，而且输出响应的信噪比对于输入噪声的变化具有&共振&形状的曲线。

When the launched SNR is more than the threshold, the cognitive network is an inter-user interference limited system, the base station selects the stochastic wave forming mode of a single beam and selects the user which has the maximum received SNR from the sub-scribers as a current communication object; when the launched SNR is less than the threshold, the sub-scriber network is a noise interference limited system. The base station selects the opportunistic SDMA of multi-beams and then selects a plurality of scribers with the maximum received SNR from the sub-scribers as the communication objects, thus realizing the maximization of system capacity.

当发射信噪比大于门限值时，认知网络为用户间干扰受限系统，基站选择单波束的随机波束成型模式，在从用户中选择接收信噪比最大的用户作为本次的通信的对象；当发射信噪比小于门限时，从用户网络为噪声干扰受限系统，基站选择多波束的机会式空分多址模式，在从用户中选择信噪比最大的几个用户作为通信对象，从而实现了系统容量最大化。

In comparison with the current version, in which the signal-to-noise ratio accuracy of the noisy signal produced is heavily influenced by 'clean' signal itself, the proposed approach has removed this unfavorable impact by choosing another factor to rescale the signal.

在目前广泛使用的加噪信号方法中，产生的信噪比精度受无噪信号的影响很大，与之相比，新方法通过选择新的因子对信号进行归一化，剔除了无噪信号对产生的加噪信号的信噪比影响。

They weren't aggressive, but I yelled and threw a rock in their direction to get them off the trail and away from me, just in case.

他们没有侵略性，但我大喊，并在他们的方向扔石头让他们过的线索，远离我，以防万一。

In slot 2 in your bag put wrapping paper, quantity does not matter in this case.

在你的书包里槽2把包装纸、数量无关紧要。